JPS60162637A - Manufacture of polypropylene resin container - Google Patents

Abstract

PURPOSE:To injection mold an expanded plate for a polypropylene resin container excellent in rigidity and mechanical strength, by using a composition containing a special polypropylene resin and a nucleating agent. CONSTITUTION:The intended expanded plate 2 has an average thickness of 0.3- 3mm., and an area of 100cm<2> or more and includes folding lines 12 and notches 13-16. The average thickness at the folding lines is about 5% or more of the average thickness of the expanded plate and is 0.1-2.0mm.. The polypropylene resin should contain 50wt% of polypropylene resin having a melt index (MI) of at least 10g/min. 0.01-2pts.wt. of nucleating agent are added to 100pts.wt. of this polypropylene resin. Thus a homogeneous expanded plate can be obtained without causing problems such as cobwebbing although a polypropylene resin good in fluidity is used. The obtained expanded plate is excellent in rigidity, Izod impact value, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to a unit of a certain volume such as a tape cassette for a video tape recorder, a floppy disk, a video disk, a digital audio disk, and a sheet of photosensitive material. The present invention relates to a method of manufacturing a thermoplastic resin container having particularly improved strength and suitable for accommodating products such as film, photographic paper, printed boards, etc.

[Prior art]

Although small-volume thermoplastic resin containers such as those mentioned above can be three-dimensionally molded by direct injection molding, for example, containers for storing items larger than a certain volume, such as tape cassettes for video tape recorders. In case of case
Since it is impossible to perform three-dimensional molding by direct injection molding, a method is used in which boxes are manufactured from expandable plates.

Conventionally, the development plate for such synthetic resin containers is made by extruding a long synthetic resin plate from a T-die, printing it if necessary, and then cutting it into a plate of a certain size. , the area corresponding to the crease (hereinafter referred to as the ``key line area'') is compressed or machined, the notch is punched out, and in some cases, the surface is foil-stamped or embossed. It was being made.

However, such conventional manufacturing methods require a large number of man-hours, are inefficient, lack uniformity in the strength of the silicon wire, surface shape, thickness of the developed plate, etc., and have a high incidence of defective products in terms of quality. In addition, because the wires, shaping, and cutting were done forcefully, the wires were cracked, the surface of the wire grooves was rough, and the appearance was poor due to the adhesion of debris to the cut surfaces, resulting in cutting allowances. Since Kirikuyo was disposed of, there were inconveniences in terms of cost and industrial waste generation. Furthermore, in terms of quality, notches and other punched edges are crushed and cut scraps are generated, which fall off during use, and when storing video cassettes, for example, these adhere to the tape and drop. It was also impossible to process special shapes and fine lettering and shape embossments.

In order to eliminate the drawbacks of the prior art as described above, the present inventor previously proposed the production of such a synthetic resin expansion plate by injection molding (Japanese Patent Application No. 58-260).
No. 07). In other words, it has been considered difficult to injection mold a deployable plate with a wide area beyond a certain level using resin, and no attempt has been made to do so, but it is now possible to make a deployable plate with a diagonal line or notch by injection molding. We have also found that by doing so, the drawbacks of the prior art as described above can be completely eliminated.

The spread plate formed by the above method has an average thickness of about a3 to 3
-, the area is 10051 mm or more, and the average thickness of the diagonal line part is about 5 mm or more thinner than the average thickness of the expansion plate, and the average thickness of the diagonal line part is about 11 to 2.0 mm. When making a flat plate-shaped development plate with such a line part by injection molding, the gate position and resin composition are not a problem, and the molten resin must spread uniformly and quickly to the molding cavity. Must be.

For this purpose, resins that have good fluidity (high melt index) when melted are preferable, but using such resins may cause stringiness during molding,
There are drawbacks such as slightly inferior strength of the molded product.

On the other hand, since the box body is assembled by forming the expandable plate and then folding it at the wires, the expandable plate must be strong (high rigidity). Polypropylene resin is suitable for this purpose, but there are some problems with the deformation resistance of the molded product and the Izot impact value. It is required to have characteristics such as no deformation such as twisting or warping when fixed, and a high Izot impact value when used as a container.

Furthermore, depending on the container, it may be necessary to make the entire container or a portion thereof, such as a window, transparent, and a resin composition with good transparency is required to be used.

[Purpose of the invention]

As a result of various studies on injection molding methods that meet the above requirements, the inventors of the present invention have obtained a container that meets the above requirements by using a composition in which a nucleating agent is added to a special polypropylene resin. They were very successful in achieving the present invention.

Accordingly, the present invention provides a method for manufacturing a polypropylene resin container with excellent mechanical strength such as rigidity and Izod impact value by injection molding using a polypropylene resin having good flowability.

Another object of the present invention is to provide a method for manufacturing polypropylene resin containers by injection molding, which uses polypropylene resin with good flowability and does not cause troubles such as stringing during molding.

Still another object of the present invention is to provide a method for manufacturing a container made of polypropylene resin, which has excellent transparency in whole or in part.

[Structure of the invention]

The present invention mainly relates to a method for producing a container made of polypropylene resin, which comprises producing a spread plate having a diagonal line part and a cutout part by injection molding, and manufacturing the same, in which the polypropylene resin is 100
50% by weight of a polypropylene resin containing 1101 to 2 parts by weight of a nucleating agent and having a melt index (MI) of at least 10 t/10 min.
This is a method for manufacturing a polypropylene resin container characterized by comprising the above steps.

In particular, the present invention is a polypropylene resin in which the average thickness of the developing plate is about α3 to 3, and the average thickness of the silicone line part is about 5% or more thinner than the average thickness of the developing plate, and about α1 to 2.0. Suitable for manufacturing containers.

The present invention will be explained in detail below.

The development plate produced according to the present invention has an average thickness of 13 to 5 cm, an area of 100 cm or more, and has a wire and a notch as described later. The average thickness of the K wire is about 5% or more of the average thickness of the development plate, and +lL1~2.0■,
In particular, [115 to t5m.

The polypropylene resin used in the present invention has a melt index (MI) of at least 10 f/min.
Contains 0% by weight or more.

The melt index (MI) used in the present invention is
J engineering sx 7210 (A87MD 123B -62
According to 7), using an extrusion type plastometer, the major axis Z1m
, Orice of length 8m+ is 2.16 to 25 with a load movement of 9.
The outflow amount when the melted resin was allowed to flow out at 0° C. was measured and expressed in units of 2710 minutes.

Polypropylene resins with an Ml of 10t/1 [1 minute or more] used in the present invention include homopolypropylene, propylene/ethylene block copolymer, propylene/ethylene 2y dumb copolymer, propylene and C-010α olefin copolymer, chlorinated polypropylene, crosslinked polypropylene A single or a mixture of two or more of these can be used.

In the present invention, 50% by weight of other thermoplastic resins may be included together with the polypropylene resin having an MI of 10 f 710 min or more as described above. Low-density polyethylene (IIDP]!+), low-pressure low-density polyethylene (L-LDPIll), medium-density polyethylene (MD
PK), high density polyethylene (HDPI!+), copolymers of ethylene and other thermoplastic resins such as ethylene/ethyl acrylate copolymers, ethylene/vinyl acetate copolymers, ionomers, etc. alone or in combination of two or more polyolefin resins can be used.

In the present invention, the polypropylene resin 10 as described above is used.
By adding α01 to 2 parts by weight of the nucleating agent to 0 parts by weight, the above-mentioned cut line can be formed without causing problems such as stringiness, even though polypropylene resin with good fluidity is used. A homogeneous developing plate having notches can be obtained, and the obtained developing plate has excellent rigidity, Izot impact value, etc. In addition, by mirror-finishing a desired part of the inner surface of an injection mold, that part can be made extremely transparent, and if transparency is not required or there is a part, If the entire inner surface or a necessary portion is textured or matted, it can be made opaque due to the diffused reflection effect.

Nucleating agents used in the present invention include carboxylic acids, dicarboxylic acids, anhydrides and salts thereof, salts or esters of aromatic sulfonic acids, aromatic phosphinic acids, aromatic phosphonic acids, specifically P-t - Aluminum butylbenzoate, aluminum salt of aromatic carboxylic acid, aromatic carboxylic acid, metal salt of aromatic phosphate, condensate of polyhydric alcohol and aldehyde, 1. 2.4-Dibenzylidene sorbitol, a di-substituted benzylidene sorbitol compound represented by the following formula (wherein R is either alkyl having 1 to 8 carbon atoms, alkoxy or halogen, and is different within the same compound) stearyl lactate metal salts such as calcium or magnesium stearyl lactate, N-(
Alkylamine compounds represented by the following formula, such as
are each independently an integer between θ and 1o, and k+4≧1. ), 1.2- and lithium salt, sodium salt, potassium salt, calcium salt, i
Hydroxy-stearic acid metal salts such as magnesium salts, 8 carbon atoms such as stearyl alcohol and lauryl alcohol-λ
~3o alkyl alcohols, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, alkali metal oxides such as sodium oxide, lithium carbonate, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, and carbonic acid. Carbonates of alkali metals such as potassium hydrogen,
Alkaline earth metal hydroxides such as calcium hydroxide, magnesium hydroxide and barium hydroxide, alkaline earth metal oxides such as calcium oxide, sodium benzoate, benzoic acid, sebacic acid and other known nucleators. These nucleating agents may be used alone or in combination of two or more of these nucleating agents.

The present invention further includes various known additives (various white pigments,
(color pigments, color dyes, antistatic agents, metal powders, lubricants, ultraviolet inhibitors, antioxidants, electromagnetic shielding substances, fillers, inorganic or inorganic fibers, etc.).

EMBODIMENT OF THE INVENTION Hereinafter, the embodiment of producing the expansion plate by this invention is demonstrated with reference to drawings.

In the present invention, as shown in FIG.
It is manufactured by box-making the expansion plate 2 shown in the figure.

In FIG. 2, the polypropylene resin development plate 2 includes a front part 4, a back part 5, a left side part 6, a right side part 7, a bottom part 8,
A polypropylene resin container 1 as shown in FIG. 1 is formed by forming the left side overlapping part 9, right side overlapping part 10, flaps 11, 111L, and key line part 12 into a box. . In FIG. 1, the correspondence of each part of the development plate in FIG. 2 is shown except for the 7 laps 11, 11a and the highlighted portion 12.

Conventionally, in cases where a container 1 made of thermoplastic resin as shown in FIG. After imposition printing and drying, cut it and cut out the notches marked with diagonal lines in Figure 2. After making the plate into a rectangular shape with no slanted lines, the cross-lined portion 12 is formed by compression shading or cutting, and then diagonally lined notches 13, 14.
15.16 is punched and in some cases, the front part 4
etc., to create a development plate, which was then manufactured into a box.

According to the present invention, the developing plate 2 as shown in FIG. 2 is formed by injection molding into a polygonal shape having a cutout portion, a diagonal line portion 12, and, depending on the case, an uneven front portion. This is prepared, and after printing or the like is applied to it if necessary, it is made into a box to produce a polypropylene resin container 1 as shown in FIG.

In the method of the present invention, various polypropylene resins can be used as the polypropylene resin used in injection molding, including polypropylene resins, polyolefin thermoplastic resins (including copolymers with other thermoplastic resins), Alternatively, a polystyrene thermoplastic resin, a Be-based thermoplastic resin, or a mixed resin of two or more of these thermoplastic resins is used, and in particular, a weight coefficient of 50 or more has a melt index of 1.
Thermoplastic resins, which are polypropylene resins with a sat/1o content, and propylene/ethylene, random copolymer resins are suitable for cost, printability, manufacturing accuracy, dimensional stability, wire strength, surface strength, rigidity, and injection molding suitability. It is suitable in terms of etc. In the present invention, α0
1 to 2% by weight of a nucleating agent is blended, but if necessary,
As mentioned above, these polypropylene resins contain various blowing agents, white pigments (titanium oxide, Merck, mica, calcium carbonate, clay, etc.), various carbon blacks, various color pigments, and various metal powders (aluminum powder, aluminum paste, etc.), various organic or inorganic fiber substances such as various metal fibers, glass fibers, and carbon fibers, various other coloring dyes, various antistatic agents, various silicones, surfactants, and sodium stearate. Various additives such as lubricants and antioxidants can be added.

Furthermore, when injection molding is performed in the method of the present invention, the injection port (gate) for the nucleating agent-containing molten polypropylene resin is not limited to one location, but can be provided at multiple locations. By doing so, the flow of the polypropylene resin is improved during injection molding, and the formation of a boundary line where resin flows converge, which is called a weld line, can be prevented. These injection ports (gates) are shown in Figure 2 on the inside of the container in order to improve the fluidity of the polypropylene resin in terms of the appearance of the container and in the structure where the diagonal line is provided only on the surface of the container as shown in Figure 5. xl * x鵞＋ ”* + Yl * Yl (
Bin gate is a typical example), or notch part 13, 14゜15
．． 16 product ends (representatively the side gates), or the front and back sides of the left and right overlapping parts 9 and 10 or the flaps 11° and 11a,
It is desirable that the polypropylene resin be formed at one or more locations on the ends, preferably in the vicinity of symmetrical positions on the left and right sides and on the top and bottom, where the polypropylene resin can flow in approximately the same amount of time to all four corners. In particular, if the polypropylene resin injection port (gate) is to be provided at only one location, it is particularly desirable to provide it at the positions X and Yl in Figure 2. Also,
If it is placed in two places, place it at the positions Yt & Ym in Figure 2.

Another example of creating two locations is xl and xl in Figure 2.
It is also desirable to place it in the position of

In any case, in the present invention, the number of resin injection ports (gates) and Since the position and shape change, the present invention is not limited to the above description, and any number or shape can be adopted at any position on the expansion plate, making it suitable for injection molding and improving the surface (visible surface) of the container when manufactured. ) is desirable from the viewpoint of appearance and fluidity of the resin.

In addition, in FIG. 2, Xi,...x4 and 7te
...y4 is the distance between each gate.

FIG. 4 is a schematic sectional view showing an example of an apparatus used for injection molding in the present invention.

In this example, a mold having one expandable plate molding cavity is illustrated, but the present invention is not limited to this. A double-stacked mold that can supply molten polypropylene resin containing a nucleating agent to both cavities at the same time,
It is possible to use a multilayer mold in which the number of cavities is further increased and molten resin can be supplied from one or two injection tubes. Further, depending on the case, a vacuum injection molding method may be adopted in which an exhaust device is provided and the cavity is evacuated before supplying the molten resin.

The illustrated mold includes a fixed mold 21, a movable mold 22, an injection cylinder 23, a shell, a cavity 24 for molding a development plate between the fixed mold 21 and the movable mold 220, and a molding cavity 24 formed in the fixed mold 21. Molten polypropylene resin is supplied to the cavity 24 from the injection tube 23 through the runner 25 .

In the present invention, 0.01 to 5 weight of a silicon compound such as polydimethylsiloxane, a surfactant such as saponin, or a lubricant such as a higher fatty acid metal salt such as stearic acid is added to the polypropylene resin together with a nucleating agent. By adding a copolymer, it is possible to improve the fluidity, moldability, and mold release properties during molding, as well as the slipperiness after molding. Also, by adding an antistatic agent to the polypropylene resin, it is possible to prevent dirt and dust from adhering to the container, or by adding a foaming agent to the polypropylene resin, the appearance of the container can be changed and the texture can be improved. Lightening may also be implemented selectively.

In the present invention, the wire portion and the notch portion (which may be shaped in various ways as necessary) are manufactured as described above.
Various printing methods (silk screen printing, offset printing, flexo printing, gravure printing,
Create a printing layer of one or more colors of each type using pad printing, curved surface printing, electrostatic transfer printing, hot stamping (foil stamping) transfer printing, inkjet printing, rotary roll printing, etc. (If necessary, use a primer to improve printability. (A protective layer may be added to protect the coating and printed surface.) After that, blow cold air, hot air,
Due to various winds, infrared rays, ultraviolet rays, electron irradiations, etc.
Assembling a continuous printing line after injection molding (possible by fixing the printing layer to the development plate) is effective in terms of production costs, reduction in inventory, reduction in printing man-hours, etc.

When manufacturing a polypropylene resin container 1 as shown in FIG. 1 by the method of the present invention, a developing plate 2 as shown in FIG.
It is preferable that the cross-sectional shape is as shown in FIG. Further, in FIG. 3, the key lines are provided only on one side of the expansion plate, but they may be provided at symmetrical positions on both sides. Plate thickness t
is generally from about αδ- to about 3-, and the silicon line portion is 5 or more, preferably 15 or more, with respect to the average plate thickness t of the developed plate.
Most preferably, by making the ink thinner by 30 mm or more, the developing plate having notches and diagonal lines can be dried or chemically reacted after printing to prevent warping or twisting even if the printing ink is rapidly fixed to the developing plate. The occurrence of this process is small, making it easy to form boxes. In the present invention, the thickness of the developing plate 2, which is an injection molded product, is limited to a3 to 3cm in order to ensure cooling efficiency, prevention of warping, sink marks, and eye wrinkles, and ensuring strength.
In order to prevent warpage and sink marks when the printing ink is fixed and to ensure the fluidity of the polypropylene resin and at the same time to facilitate box manufacturing, the wired portion should be 5 inches or more, preferably 15% or more, relative to the board thickness t.
Most preferably, it is necessary to make it thinner by 30 inches or more, and from the viewpoint of strength, it is necessary to ensure a thickness of at least α1 snow or more.

In the present invention, the front, back, entire surface or front part 4 is
, the outer or inner surfaces of the back surface portion 5, left side surface portion 6, right side surface portion 7, bottom surface portion 8, etc. are selectively embossed, grooved, and four-parted to improve the appearance and handleability. In conventional manufacturing methods, these were performed by embossing, but in the method of the present invention, these surface treatments can also be performed during injection molding.

〔Example〕

Next, in order to further clarify the effects of the present invention, examples are listed below.

(1) A double-stacked, four-cavity mold was used, as shown in FIG. 4, in which there were two expansion plate injection molding cavities on each side and an injection cylinder above. In this case, the mold was designed so that the dimensions of each developing plate were as follows. The polypropylene resin injection port (gate) is located inside the development plate in Figure 2 (
Inner bottom surface that touches the items stored in the box) Ys and Ys 2
There were several locations.

Vertical and horizontal dimensions of the expansion plate: The longest part is 247swXZS7wm Thickness of the expansion plate: 0.8m Dimensions of the lined part: Width 1.5sm, depth L25■ Cross-sectional shape of the lined part: Notch as shown in Figure 3 Section 13.1
Dimensions of 4: Approximately 70 m in length, 20 m in width Dimensions of notch 15.16: Polygon whose longest part is 37 x 28 m (2) Using this mold, molten polypropylene resin with the following composition was injection molded: Mitsui Polypropylene resin manufactured by Petrochemical ■ (M Engineering 40 f7
10 minutes) ...89.8 weight dimethylpolysiloxane manufactured by Shin-Etsu Silicone ■, KF-96 (trade name) ---
at[(amount) Titanium oxide...2% by weight Para-tertiary-butylbenzoic acid...α1% by weight Antistatic agent Electrostripper manufactured by Kao Soap■
・α1% by weight (3) Print characters in two colors, black and red, using a silk screen printing method on the injection molded development plate 2, dry it with hot air from SOC, and after fixing the printing ink to the development plate, heat it at 80°C. After applying pressure with a plate and stamping the product name with aluminum foil, it is assembled and the overlapping parts are welded using an ultrasonic welding machine, and the approximate dimensions are 192 m x 105 haze x 28 - Mechanical properties such as rigidity and Izotsu impact value A white videotape cassette case with excellent strength was produced. In this case, an extremely homogeneous spread plate could be molded in a short time without causing any stringy force during injection molding.

When the number of boxes manufactured is 300,000 pieces, compared to the conventional manufacturing method that includes cutting and punching processes, the manufacturing cost is reduced to a5%, and the incidence of defective products is reduced by ear loss, cutting/cutting loss, and cutout. The number of stitches was 1 in the method of the present invention, compared to 11 in the conventional method, including losses.

In the above example, titanium oxide was added to obtain a colored, opaque container, but if no pigment is added and the mold is finished to a mirror finish, a highly transparent container can be obtained. Similar results were also obtained when the various nucleating agents described above were used in place of para-tertiary benzoic acid as the nucleating agent.

〔Effect of the invention〕

According to the method of the present invention, it is possible to efficiently manufacture polypropylene resin containers that are uniform and have excellent mechanical strength such as rigidity, with greatly reduced warping and twisting of the unfolding plate using polypropylene resin with good fluidity. can.

The present invention is not limited to the above-mentioned embodiments, and can be widely applied, for example, as shown below.

(1) The shape of the expansion plate is not symmetrical; for example, the shape of the front part and the shape of the back part may be different.

(2) Even if the thickness of the side part is the same as the remaining thickness of the wire part, the strength can be maintained by overlapping and joining.

(3) The shape of the notch is rectangular, square, trapezoidal, semicircular,
It can have various shapes such as semi-ellipse, equilateral triangle, isosceles triangle, and arrow shape.

(4) The remaining thickness of the wire part may be partially thickened to improve the flow of resin during injection molding.

(5) The surface of the mold is processed in one or more places on the development plate.

K has a transparent window, and the inner and outer surfaces of the case are decorated with the product name, company name, picture, etc., such as outer grain, sand grain, rope grain, vertical stripes, horizontal stripes, lattice grain, fine-grain surface texture, etc. (kubo processing) ). As a specific grained ensemble, there are more than 210 types of 1 Pairon Shibo published by Tokyo Pairon ■.

(6) In injection molding, the polypropylene resin can be a copolymer or a mixed resin of two or more types of polypropylene resins.

(7) One or more types of colored pigments or colored dyes can be added to the polypropylene resin.

(Injection molding of 83 development plate (including vacuum injection molding in all molds)
After that, a printing process and a two-bell pasting process can be selectively added before and after the box manufacturing process to add marks and letters.

[Brief explanation of the drawing]

Fig. 1 is an external view showing an example of a polypropylene resin container manufactured according to the present invention, Fig. 2 is a plan view of the unfolding plate, and Fig. 3 is a sectional view of the unfolding plate taken along plane A-B in Fig. 2. , FIG. 4 is a schematic sectional view showing an example of an injection molding apparatus used in the present invention. 1...Polypropylene resin container 2...Development plate 12
...K line part 13-16...Notch part xi * x
l * xl + Yl * YS”・Gate 21・
...Fixed mold 22...Movable mold 23...Injection tube 24...Cavity for molding the development plate (and 3 other people) Fig. 1 Fig. 25!1 Fig. 3

Claims (1)

[Scope of Claims] 1) A method for producing a container made of polypropylene resin, which involves producing a developing plate having a diagonal line part and a notch part by injection molding, which is mainly made of polypropylene resin, and then drawing the same. , the polypropylene resin contains 0.01 to 2 parts by weight of a nucleating agent based on 100 parts by weight of the resin, and the polypropylene resin contains 50 parts by weight of a polypropylene resin having a melt index (M) of at least 10 f710. A method for producing a polypropylene resin container, characterized by: 2) The average thickness of the developing plate is 0.3 to 3 m, the average thickness of the diagonal line part is 5 times or more thinner than the average thickness of the developing plate, and the average thickness of the diagonal line part is (11 to 2 m). The method for producing a polypropylene resin container according to claim 1), wherein the container is made of cod.